/Engine/Source/Runtime/Engine/Classes/Particles/Trail/ParticleModuleTrailSource.h
Retrieve the SourceOffset for the given trail index. Currently, this is only intended for use by Ribbon emitters
bool true if successful, false if not (including no offset)
bool ResolveSourceOffset ( int32 InTrailIdx, [FParticleEmitterInstance](API\Runtime\Engine\FParticleEmitterInstance) * InEmitterInst, FVector & OutSourceOffset )